Front-firing gun perforator



United States Patentf) Jr, Lynwood, Califi, assignors:to B. J. Servicelno,

Long Beach, .Calif., a corporation of Delaware I Application December 3, 1951, SerialNo. 259,586

16 Claims. (Cl. 1645) This invention relates to well bore or casing perforators of the type from which bullets are explosively proected to'pierce the casing and/r surrounding format on to promote fluid flow. More specifically the invention relates to the'design, construction and arrangementof individual gun units for 'such perforators together Wllhlhfl corresponding design; construction and arrangement'of-carriers for such unit. The invention is particularly concerned with the "firing mechanism of such devices and provides-means, whollycon'tained within the carrier,-whereby each unit may be discharged'by a detonator located in front of the bullet within its barrel:

For many years the perforation of-we'llbores and casings by explosively projected-bullets has been accepted as standard practice and'numerous and varied types of guns have beendevised to meet the numerous and varied problems encountered. Since the-inception of this 'concept and throughout the continuously increasing use of this practice the trendhas been toward devices com* prising a carrier in which is mounted individual gununits each including a firing chamber and bullet barrel, such units being adapted for preload'ing with propellant charge and piercing bullets before" assembly with-the carrier.

Amongztheproblems encountered is that of the ignition; of .the' propellant charges Since external 'firing systems such: as: electrical conductors; fuses and'mechanical' percussion devices are subjected to attack by thewell fluid and'deterioration due'to hi'gh'temperatures and pres sures as well as'mutilation "and damageby mechanical action such :as abrasion, various internal firing arrange ments have been suggested. Fuselike explosive priming cord has been favorably accepted'as the firing devicein many=:instances.- Such cords extend Within the carrier toithe successive gun units wherein the propellant charge,

behind-the bullet, is ignited either-directly by theprim-' ing cord or through the intermediate agency of a prim ing caplor booster charge also located behind the bullet.

However, space is at a premium in all types of well perfo-- rating guns since/the length of the gun is of course limitedv by the diameterof the Well bore or casing; .Where the bullet type gun is fired by a fuse and cap or boosterlocated rearwardly'ofthe propellant it is of course necessary torestrict the barrel length in advance of the bullet to. compensate for the space taken. by such firing mechanism behind the propellant. Since barrel length is an important factor in ballistic efiiciency it has been an object in the design of such guns to minimize the space required rearwardly'of the bullet in order to increase the barrel length in advance thereof.

One means employed as an expedient for providing maximum'barrel length is that'of discharging the propellant'by use of a detonatorIlocated-within the barrel in advance'of the bullet. Such'detonators act through the bullet by shock, heat or compression, 'ora combination thereof, to ignite the propellant behind the bullet which, thereupon discharges the-bullet forwardly through the barrel. Such guns are commonly designated as front-firing guns-and have achieved eminent success and are widely considered as of superior efficiency to'that of-the rear-fired type. Such efficiency has been attributed not only to the maximum barrel lengt-h obtained butalso' byvirtue-ofan excess compression of-the propellant charge, by-rearward movement of thebulletupon 'deto- 2,695,665 Patented Nov. 30, 1954 nation whereby explosion thereof is more spontaneous and uniform throughout the charge particles as distinct from the slower progressive burning of the propellant ofth' rear-fired 'guns.

Since the detonator for front-firingguns is located in thebarrel in advance of the bullet andreadily acces It is therefore among the primary objects of the present invention toprovidea novel, simpleand improvedperforating gun, the combination and interrelati0n-of parts of which are such as to provideefiiciency and effectiveness with strength and' durability while-insuring ease of assembly and economy of manufacture.

Another object of the invention is to provide individual gun units for assembly in a unit carrier the design; construction and arrangement of which are such asto insure effective and effieient operation thereof while pro-- viding fortheir mounting with a carrier in a novel, simple and improved manner.

A further object is to-provide a perforating gun carrier the design; construction and arrangement of which is suchas tocombine and cooperate with gun units mountedtherein'to insuresecurity of mounting as well asfacility of assembly and 'disassembly;

It is also an object of the-invention to provide-connbining and cooperating .unit and carrier constructions whereby the interior of the carrier will be securely sealed upon the mounting of the units-within the carrier was to provide for the safe location therein of firing meansfor the units.

A primary object of equal importance is to provide a structure and arrangement for the front firing of gun units by a firing mechanism sealed within the carrier.

More specifically it is an object of the present invention'to provide gununits-for a perforating gun carrier which may be readily assembled and disassembled with the carrier and which provide for a front firing .of the propellant charge thereof while insuring fluid-tight and pressure resistant sealing of the firing mechanism thereof within the carrier.

With the foregoing it is the corollary object of provid-' ing a novel and improved carrier for self-contained front-firing gun units which in combination therewith provides for a sealed and internally mounted firing mechanism.

Numerous other objects and features of the invention may'be defined as including a hollow cylindrical carrier formed with spaced means for sealingly mounting'individualperforating units therein and individual gun units,- each comprising a substantially cylindrical body having means cooperating with the carrier for sealingly retaining the units therein together with means to be enclosed by the carrier for firing the units.

piece to be mounted within the carrier recess and-a neck engageable' by the port to sealingly mount the unit within the carrier. An important'feature of the invention is the The carrier is formed with an internal-unit engaging recess and a diametrically opposite port receiving aperture While each unit includes -a tail combining structure of the neck and port permitting entrance therebetween of an explosive priming cord whereby the propellant of the unit may be ignited by a detonation Within the barrel thereof in advance of the bullet and by which the entire cord may be enclosed within the carrier and protected thereby.

Referring to the drawings illustrating one preferred embodiment of the inventive concept the numeral indicates the carrier body which comprises a long cylindrical pipe or tube of substantial wall thickness and of an external diameter such as to be readily accommodated in the well bore as casing to be perforated. The carrier body is not limited as to dimensions, the length being best determined by the number and arrangements of gun units to be mounted therein, it being understood that such units are longitudinally spaced and preferably oriented to form a spiral shot pattern in the bore or casing. The external diameter is largely determined by the internal diameter of the bore or casing through which the gun is to be lowered. Preferably maximum diameter permitting easy insertion and withdrawal is selected in order to obtain a desirable internal diameter while insuring adequate strength through wall thickness and to insure maximum barrel length. However, in some instances the casing or bore are of such diameter as to present no limitation on the carrier and in fact the modification of Fig. 3 is designed to provide increased barrel length where the bore or casing diameter substantially exceeds that of a conventional carrier. The thickness of the carrier wall is determined by the quality and strength of body material and regardless of body diameter is such as to insure such strength as to withstand the shock of the firing of the gun units without fracture or distortion. Preferably the carrier body is formed of steel not only to withstand shock and abrasion but to resist the deleterious effects of heat, pressure and corrosion encountered within the well formation. However, the invention is in no way limited to such material and the body may in fact be expendable, the material selected being such as to wholly or partially distintegrate in use.

The wall of the carrier 10 is formed with longitudinally spaced gun apertures 11, preferably disposed in spiral formation, such apertures consisting of an inner threaded bore 12 and an enlarged outer counterbore 13 between which is formed a sealing seat 14. The apertures 11 are here shown as angularly oriented at 120 degrees with respect to each other and longitudinally spaced at intervals approximately 3 times their diameter. Such spacing and orientation is by no means critical and may vary widely as preference dictates. In some instances the apertures may be more tightly spiralled or, if desired, they may be in alignment to pierce the bore or casing in a straight line and the longitudinal spacing may be as close together as the diameter of the apertures permit or may be separated by a foot or more of intervening carrier wall.

In diametrical alignment with each aperture 11 the inner wall of the carrier 10 is formed with a recess here shown as circular and of but shallow depth. The recesses 15 are preferably concentric with the bores 12 and 13 being adapted to receive the reduced and conforming tail piece of the gun unit hereinafter discussed in detail. As with the thickness of the carrier wall the depth of the recess 15 is not critical; it is however so proportioned with respect to the wall as to insure adequate wall thickness between the outer surface of the carrier and the floor of the recess to withstand firing shock. Since, as will hereinafter be seen, the unit fits within the recess with its tail piece abutting the recess floor, recoil shock is borne directly by the wall at or adjoining the recess so that substantial thickness in this zone is desirable. As here shown the recess 15 is circular, conforming with the circular configuration of the tail piece. Other related and interfitting configurations may of course be elected if desired, the primary function of the recess being to support the rear end of the gun unit in parallel alignment with its corresponding part 11.

The gun unit, generally indicated by the numeral 16, comprises a substantially cylindrical steel body having a central section 17 of uniform and maximum diameter, a rear frusto conical taper 18, and a circular tail piece 19 for fitting within the recess 15. Forwardly of the central section 17 the body includes a forward frusto-conical taper 20 terminating in a cylindrical neck 21, the outer terminal end of which is formed into semi-circular facing walls 22 by diametrically opposed longitudinally extending priming cord slots 23. Extending inwardly from the forward end of the unit there is provided a centrally disposed uniform longitudinal bore 24 forming a firing chamber 25 terminating within the rear frusto-conical taper 18 and a barrel 26. As will be noted the frusto-conical rear taper 18 in combination with the extended tail piece 19 forms a substantially uniform wall thickness for the firing chamber and inner end of the barrel thus insuring adequate mass encompassing the explosion zone.

The propellant charge indicated by the numeral 27 is of course located within the firing chamber 25 and is sealed therein, preferably under an initial pressure, by the butt end 28 of the perforating bullet 29. The nose 30 of the bullet is encircled by a restraining ring 31 preferably of lead which secures the bullet against inadvertant movement from the barrel, retains the bullet pressure against the charge 27, provides for a build-up of propellant force before outward movement of the bullet in its discharge from the barrel and acts as a lubricant and seal as the bullet is projected. The characteristics of the charge, bullet and restraining ring may all be conventional and vary as dictated by the type of perforation desired. Various kinds and charges of propellant may be employed, the bullet may be of any selected type and the restaining ring may be of any form desired or may be omitted if preferred.

For retaining, supporting and sealing each gun unit within the carrier there is provided a port or cap generally mdicated at 32 in Figs. 1 and 2. The port 32 is circular to fit the circular aperture 11 and includes an inner externally threaded skirt 33 adapted to threadedly engage the threads of the bore 12, as well as a flange 34 extending outwardly of the skirt to fit the bore 13 and forming a seat 35 adapted to face the shoulder 14. An 0 ring or like seal 35a is located between the shoulder 14 and seat 35 to seal the interior of the carrier from ingress of formation fluid. The skirt 33 is formed with an internal inwardly facing frusto-conical recess 36 which encircles the neck 21 of the gun unit and is spaced therefrom by a transverse annular wall 37. The wall 37 extends inwardly from the smaller end of the frusto-conical recess to a central counterbore 38 forming a seat for the terminal end of the gun unit. Communicating with the counterbore 38 is a central bore 39 constituting an extension of the gun unit barrel. In assembly it will be noted that the depth of the counterbore 38 is substantially less than the inward extension of the slots 23 of the neck of the gun unit. The diameter of the neck is however approximately equal to the diameter of the counterbore 38 so that the neck will snugly fit within the counterbore leaving the inner ends of the slots 23 exposed to form a cross channel 40 through the neck opening into the recess 36.

The outer face of the port plug 32 is of general convex form to provide contour conformity thereof with the surface of the carrier. An external central counterbore 41 concentric with the bore 39 forms a seat 42 at the junction thereof upon which is disposed a fluid sealing disk 43 precluding ingress of formation fluid to the barrel of the gun unit or therefrom through the passage 40, to the intenor of the carrier. While the sealing disk 43 may be of any desired material, a brass disk is believed preferable as being easily pierced or dislodged upon emergence of the bullet, being easily forced and expanded into sealing engagement and being resistant to attack by formation fluid. As here shown the seal may be seated upon the shoulder 42 by a punch forming the indentations 44 as indicated. Threaded application and removal of the port is provided for by use of a spanner wrench the pins of which may engage the diametrically opposed recesses 45 of the outer face of the cap.

The gun units of the present invention are designed for front firing by an explosive priming cord 50 which extends continuously from unit to unit. At each unit the.

cord enters under the skirt 23 and extends across the recess 36 passing through the channel 40 to lie across the barrel section 26 in advance of the bullet. For ignition by that portion of the cord located within the barrel there is provided a detonator 51 preferably contacting the nose of the bullet and within such proximity to the fuse cord as to be ignited thereby. If desired a booster charge may be afiixed to that portion of the cord disposed within the barrel to insure firing of the detonator 51.

It will be understood of course that the detonator, upon ignition, creates shock, heat and pressure, any or all of able so thatthe firing of the'individual gun units is sub-' stantially concurrent. Where'an explosive cord is selected that portion of the cord disposed within the barrelrnay provide suflicient detonation avoiding the necessity of the separate detonator 51. The presentstructure, however,

lends itselftoalternate firing means, such as an electrical conductor having a series arrangementof thermal igniters disposed in each barrel.

Referring to Fig. '3 of the drawings it will be seen that the basic structure, as above discussed, lends itself to ap propriate modification, such as the extension of the plug or cap body beyond the outerjsurffa'cejof the carrier. In this form of the invention the elongated body portion 60 spaces the sealed end of the cap from the forward, end of theunit barrel so as to form an extended barrel the muzzle of which willilie' closely adjacent the wall of a casing or borehole the diameter of which substantially. exceeds the diameter of the'carrier. While such an extended barrel increases the 'efliciency of the grip unit, the extension serves the more important function of bridging the otherwise fluid filled space between the carrier and the formation. Since passage of the bullet through even limited areas of formation fluid greatly retards its progress and diminishes its piercing ability the extended port plug of Fig. 3 is a valuable asset in the perforating of bore holes or casings of large diameter.

In assembling the present units with the carrier each unit may be inserted through its individual aperture. Its tail piece 19 is seated within the recess 15 and thereafter the cord 50 is passed between the spaced ends 22 of the neck to lodge in the channel 40 formed by inner end of the slot 23. Thereafter the port 32 is threaded into position its counterbore 38 in axial alignment with the recess 15 and receiving in fitted relation the neck 21 of the gun unit. Upon such fitting of the neck within the recess the outer ends of the slot 23 are closed to secure the cord 50 within the channel 40. As the plug is screwed firmly in place the seal 35* engages the shoulder 34 to seal the interior of the carrier. It will of course be noted that such assembly is quick and simple and requires no special tools or equipment. After firing disassembly may be accomplished with equal ease and facility and hence loading and unloading of the carrier may be conveniently effected at the well site.

From the foregoing it will be seen that the present invention provides a novel, simple and improved carrier and gun unit as well as a novel and improved combination therebetween. It will of course be understood that the invention is in no Way limited to the specific structural details herein set forth by way of illustration and that in the practice thereof numerous changes, modifications and the full use of equivalents may be resorted to without departure from the spirit or scope of the invention as outlined in the appended claims.

We claim:

1. A perforating gun carrier comprising a longitudinally hollow body having an aperture through the wall thereof, means for mounting the front end of a gun unit adjacent said aperture, means formed by the inner wall of said body to mount the rear end of a gun unit within said body to dispose said unit in alignment with said aperture and means for securing a firing mechanism enclosed within said body and transversely of the front end of a gun unit mounted therein.

2. A perforating gun carrier comprising a longitudinally hollow cylindrical body having apertures formed in the wall thereof, means for removably mounting the front ends of gun units adjacent said apertures, means formed by the inner Wall of said body to removably mount the rear ends of said units within said body to dispose said units in alignment with said apertures and means for securing a firing mechanism enclosed within said body and transversely of the front end of the gun units mounted therein.

3. A gun port for the gun unit aperture of a perforating gun comprising a body having means for releasably engaging the gun unit aperture of a carrier, an aperture therethrough for registration with the barrel of a gun unit, a seal for said aperture, means for engaging the front end of a gun unit to locate the barrel bore thereof in registration with the aperture of the port, and a recess adjacent said engaging means for receiving and guid-ing'a'firir ig' device for a gun unit engaged by said means.

4. A gun port for the gun unit aperture of a bullet type front-firing gun perforator comprising a circular threaded body adapted to threadedly and sealingly engage the 'interadapted to receive the barrel of a gun unit and to locate the same with its barrel bore in registration with the barrel extension bore of said portand a recess formed adjacent said counterbore for receiving and guiding a priming cord to the barrel bore of a gun unit engaged by said port. I

5. A gun unit for a perforating gun carrier comprising a body, a firing chamber and bullet bore formed within said body, a tail piece at one endof saidbody adapted to be supported by means within a carrierfa barrel at the other end of the body adapted to be mounted adjacent a gun unit aperture of said carrier and means for receiving a firing device transversely through said barrel.

6. A gun unit for a perforating gun carrier comprising a generally cylindrical body, a firing chamber and bullet bore formed within said body, a circular reduced tail piece at one end of said body adapted to be supported by means within a carrier, a circular reduced barrel at the other end of the body adapted to be mounted adjacent a gun unit aperture of said carrier and means for receiving a firing device transversely through said barrel.

7. A gun unit for a perforating gun comprising a generally cylindrical barrel having a circular reduced tail piece at one end, a circular reduced barrel at the opposite end, an axial uniform bore extending inwardly from the end of the barrel and terminating short of the tail piece, said bore forming a firing chamber and a bullet barrel, a propellant charge in said firing chamber, a bullet in said bullet barrel and a detonator for said charge exltjerfiiing transversely through said barrel in advance of said u et.

8. A front-firing gun unit for a gun perforator comprising a body, a firing chamber formed within said body, a bullet barrel communicating with said chamber, said barrel including a transverse opening therein to receive a priming cord transversely thereof to dispose a portion of said cord transversely of the barrel opening.

9. A front-firing gun unit for a gun perforator comprising a body, a firing chamber formed within said body, a bullet barrel communicating with said chamber, said barrel including a pair of diametrically opposite slots extending inwardly from the open end of said barrel to receive a priming cord therethrough to dispose a portion of said cord transversely of the barrel opening.

10. A front-firing gun unit for assembly in a gun carrier of a bullet type well perforating gun comprising a generally cylindrical body, a circular reduced tail piece extending from one end of said body, a circular reduced barrel extending from the opposite end of said body, a uniform axial bore extending inwardly from the barrel and terminating short of said tail piece to form a firing chamber and a bullet barrel, a propellant charge in said firing chamber, a bullet in said barrel in advance of said charge and a priming cord in said barrel in advance of said bullet, said barrel having a pair of diametrically opposite slots extending inwardly of the barrel opening to receive the priming cord therethrough.

11. A gun unit assembly for a front-firing bullet perforator comprising a gun unit having a barrel, slots extending inwardly from the open end of said barrel and a port member engageable with the open end of said barrel to close the outer open end of said slots.

12. A gun unit assembly for a front-firing bullet perforator comprising a gun unit having a barrel, diametrically opposite slots extending in a parallel axial direction inwardly from the open end of said barrel and a port member engageable with the open end of said barrel to close the outer open end of said slots, said port member including a recess surrounding said barrel to receive a firing device extensible through said slots.

13. In a gun unit for a bullet perforator the combination, with a gun unit body having a barrel including a pair of inwardly extending outwardly open slots, of a gun port having a barrel receiving recess adapted to close the open end of the slots and including a recess'surrounding the barrel adjacent said slots to receive a firing device extensible through said slots.

14. A front-firing bullet gun perforator assembly including an apertured carrier, apertured gun ports mounted in the apertures of said carrier, front-firing gun units located within said carrier with their barrels supported by said ports and cooperating means formed on said ports and barrels for mounting a priming cord within said carrier and across the bullet bores of said barrels, to intersect the front ends of said barrels.

15. A front-firing bullet gun perforator assembly including an apertured carrier, apertured gun ports mounted in the apertures of said carrier, front-firing gun units located within said carrier with their barrels supported by said ports and cooperating means formed on said ports and barrels for disposing a priming cord across bullet bores of said barrels within said carrier, said means including oppositely disposed inwardly extending slots in said barrels and slot closure means formed on said ports.

16. A front-firing bullet gun perforator comprising a cylindrical hollow carrier having a spirally arranged series of apertures, gun ports removably mounted in said apertures to receive and support the barrel of a gun unit,

means for sealing the port with respect to the carrier to preclude the ingress of well fluid therebetween to the hollow carrier body, means on the inner wall of said body opposite each aperture thereof for supporting the rear end of a gun unit to act with the port in removably mounting a gun unit transversely of said carrier and in alignment with a port, a gun unit transversely supported between said port and said means on the inner wall of said body comprising a gun unit body having a tail piece engageable with said means and a barrel engageable with said port said barrel having inwardly extending priming cord receiving slots at the end thereof and said port having means for closing the ends of said slots to secure a priming cord therein and across said barrel.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,200,683 Schlumberger May 14, 1940 2,328,308 Turechek Aug. 31, 1943 2,334,931 Johnson Nov. 23, 1943 2,509,657 Tow May 30, 1950 2,517,560 Hambly Aug. 8, 1950 2,565,788 Tow Aug. 28, 1951 

